Micro-Particle Production

As reported later in Chapter 9.9 of this book, active-ingredient-containing polymeric micro-particles are widely used in technological and medical applications. For example, these particles are suitable as drug-delivery devices and can control the pharmaceutical release-rate over time. The particle size is absolutely important when dealing with drug-delivery devices. Very small particles can be inhaled, while larger ones can be injected into the blood stream. Therefore, it is important to control the microparticle size in the production. 

In the latest literature, the production by supercritical techniques of pharmaceuticals-loaded bio-polymer micro-particles is widely considered [34], All of these applications take advantage of the solvent or anti-solvent power of CO2. Various techniques have been proposed so far, such as the rapid expansion from supercritical solution (RESS) [35], the gas... 

Konya, J., N. M. Nagy, and M. Foldvari. 2005. The formation and production of nano and micro particles on clays under environmental-like conditions. J. Therm. Anal. Calorimetry 79 537-543. 

Micro- and Nano-particles Production Using Supercritical Fluids... 

N ew opportunities and future directions in the area of microchannel emulsification are most likely in the areas of scale-up [140,141], encapsulation/polymeriza-tion [123, 125, 158, 164—169], rapid quenching of droplets [135], and the use of emulsions as templates for uniform macroporous particle structure formation [172]. MicroChannel emulsification is also likely to open up new opportunities with systems that are highly shear-sensitive [120, 135, 173]. The ability to scale up the process will spur new markets that require high production rates and the production of monodisperse capsules and polymer particles. Such developments will be useful in drug delivery applications and will contribute to the further quantification of micro-particle properties. Additionally, the use of monodisperse emulsions as particle templates is likely to enhance the utility of highly functional nanoparticles in need of a deployment mechanism [172]. 

The Magnetic Micro-Particle Separator (MM-PS) used in this woik is shown in Fig. 2 as it was being assembled. The structures on the skid-mount are the electromagnet, power supply and chiller. The three tanks to the right in the photo are the feed, product, and underflow vessels. 

Drug micro-particle suspensions can be milled by applying a high pressure homogenization process leading to a product called nanosuspension. 

Bleich J, Muller BW. Production of drug loaded micro-particles by the use of supercritical gases with the aerosol solvent extraction system (ASES) process. J. Microencapsulation 13(2) 131-139, 1996. 

The inventor s claim appears to overlook the fact that the oil breakdown products can be oil soluble and may not be removed via filtration alone. In addition, the breakdown of oil is not completely driven by the micro particles in the oil. Some of the polymeric materials, however, could be coalesced via special techniques and could then be filtered out of... 

The Type 2 products comprising cross-linked polymers micro-particles, highly swollen by water, have a different profile. Figure 3.10 compares the profile of Polymer B (Type 1) with Polymer D (Type 2). The cross-linked polymer shows shear thinning behaviour across a very wide range of shear rates with little evidence of either Newtonian Plateau. Both these plateau regions may exist, but the extreme limits of instrument conditions maybe needed before these are apparent on the viscosity versus shear rate graph. 

In this process, silica micro-particles in the alcogel are modified with TMS. The reaction time for modification is several hours at 60°C or several days at room temperature. After the modification, TMS modified alcogel is immersed again in ethanol, which removes the by-products inside the alcogel. 

The grain- or multigrain model consists of separate model equations for characteristic grains or micro-particles and the macro-scale pellet. The characteristic micrograin is described by the following diffusion-reaction partial- differential equation for the product species s ... 

Product particle sizes vary from standard size of 6/14 mesh—U.S. Std. Sieves to mini-size granules of 10/16 mesh—U.S. Std. Sieves for small particle blends, to micro-size granules of 14/35-U.S. Std. Sieves for use on golf course tees and greens. Approximate mm corresponding to mesh sizes are 6 mesh/3.36 mm 10 mesh /2 mm 35 mesh/0.5 mm. 

As mentioned in Section 2.2 (Fixed-Bed Reactors) and in the Micro activity test example, even fluid-bed catalysts are tested in fixed-bed reactors when working on a small scale. The reason is that the experimental conditions in laboratory fluidized-bed reactors can not even approach that in production units. Even catalyst particle size must be much smaller to get proper fluidization. The reactors of ARCO (Wachtel, et al, 1972) and that of Kraemer and deLasa (1988) are such attempts. 

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